Three major oil industry executives agreed on one thing in a pair of Senate hearings Tuesday: Someone else was to blame for the drilling rig accident that triggered the massive oil spill in the Gulf of Mexico.

The senior executives from the oil behemoth BP, the offshore oil drilling company Transocean and the oilfield services contractor Halliburton pointed fingers at each other in seeking to explain what caused the accident that set afire and sank the Deepwater Horizon rig, killing 11 people.

Getting to the bottom of the accident took center stage for a day even as BP and federal agencies sought to contain or stop the three-week-old oil spill.

BP blamed the failure of Transocean's blowout preventer and raised a new question about whether Transocean disregarded "anomalous pressure test readings" just hours before the explosion. Transocean blamed decisions made by BP and cited possible flaws in the cementing job done by Halliburton. And Halliburton said that it had faithfully followed BP's instructions and that Transocean had started replacing a heavy drilling mud with seawater before the well was sealed with a cement plug.

Senators, striving to become fluent in the language of offshore drilling technology, pressed the executives to explain the failures of the exploration well and pressed BP America's president, Lamar McKay, to explain the precise meaning of his pledge that BP would pay "all legitimate claims" stemming from oil spill damage.

Lawmakers opposed to wider offshore drilling said they were sadly vindicated. "The bottom line is: If you drill in the ocean, an oil spill cannot be a surprise," Sen. Frank Lautenberg (D-N.J.) said. "All it takes is one oil spill to destroy a coastline."

Lawmakers who favor offshore drilling worried about the damage that could be done to public support. "We need the oil that comes from offshore to keep this economy moving," Sen. Mary Landrieu (D-La.) said, arguing that one-thousandth of 1 percent of oil produced had been spilled. Sen. Lisa Murkowski (Alaska), the ranking Republican on the energy committee, said that "under anyone's most optimistic scenario, our nation will need oil and gas for a long time to come."

McKay placed blame for the accident squarely on Transocean. That company, "as owner and operator of the Deepwater Horizon drilling rig, had responsibility for the safety of all drilling operations," he said.

"We don't know yet precisely what happened on the night of April 20, but what we do know is that there were anomalous pressure test readings several hours prior to the explosion," he added in a new disclosure. "These could have raised concerns about well control prior to the operation to replace mud with seawater in the well in preparation for the setting of the cement plug."

McKay also repeated BP's complaint that if all else failed, Transocean's blowout preventer (BOP) should have cut off the well, although several lawmakers noted that while BP has called the BOP a "fail-safe" device, many of them had failed in shallower waters or on land.

Transocean chief executive Steven Newman said the blowout preventers "were clearly not the root cause of the explosion." He said that by April 17, the well had been completed and the blowout preventer was ready to be moved off site. "The attention now being given to the BOPs in this case is somewhat ironic, because at the time of the explosion, the drilling process was completed," he said.